The present invention relates to ingress-egress monitoring systems for use in preventing persons, such as wanderers, whose behavior needs to be watched from egressing from an institution of protection or other specified area or from entering a dangerous area or like specified area.
At hospitals and like institutions, it has been practice to restrain the behavior of mentally handicapped patients as by confining those with a serious illness in rooms in order to prevent the patients from going out of the institution without permission. It is desired in recent years to develop ingress-egress monitoring systems which are adapted to keep watch against wandering patients without restraining patients more than is necessary.
However, such a ingress-egress monitoring system must watch over a large number of patients to monitor their egress from gates provided at a plurality of locations, while when some patients passed through one gate at the same time, these persons need to be identified individually, so that the system has the problem of becoming complex in construction.
Accordingly, an object of the present invention is to provide an ingress-egress monitoring system of simple construction which is adapted to watch over many people to monitor their ingress into a specified area or their egress from the specified area and which is further capable of identifying a plurality of persons individually when these persons passed through the same gate at the same time.
The present invention provides an ingress-egress monitoring system which is characterized in that the system comprises:
transmitters disposed respectively at a plurality of ingress-egress gates of a specified area for emitting radio waves to the respective gates,
tags to be attached to respective persons to be checked for ingress or egress and each adapted to transmit an identification signal containing an ID code of its own in response to radio waves received from the transmitter,
receivers disposed respectively at the ingress-egress gates for receiving the identification signal from the tag and each operable to output a monitoring signal containing the ID code contained in the identification signal and the number of the gate of its own, and
a monitor connected to the receivers for detecting an incidence of ingress into or egress from the specified area based on the monitoring signal output from the receiver,
the tags to be attached to the respective persons being operable to transmit the respective identification signals in cycles different from one another.
With the ingress-egress monitoring system of the present invention, tags are attached to all wanderers. The monitor is installed, for example, in a janitor""s room. If a wanderer has passed through one of the ingress-egress gates, radio waves emitted from the transmitter provided at the gate are received by the tag on the wanderer, whereupon the tag prepares an identification signal containing the ID code of its own and transmits the signal toward the receiver.
In response to the identification signal, the receiver prepares a monitoring signal containing the ID code contained in the identification signal and the gate number of its own and feeds the monitoring signal to the monitor. Based on the monitoring signal output from the receiver, the monitor detects the ingress into or egress from the specified area and outputs the ID code and the gate number contained in the monitoring signal. The janitor can therefore identify the wanderer with reference to the ID code and also identify the gate through which the wanderer has passed with reference to the gate number.
For example, upon two wanderers passing through the same gate at the same time, two tags transmit their identification signals at the same time, but the receiver is unable to normally receive the identification signals due to interference. However, since these signals are transmitted in different cycles, the identification signals in the subsequent cycle are produced at different times, and the signals transmitted from the two tags can be received normally. Consequently, the persons passing through the same gate can be individually identified on the monitor.
Stated more specifically, the tags are set for different identification signal transmission cycles in advance. Further in transmitting the identification signal, each of the tags produces a random number and is set for the transmission cycle based on the random number. The cycle for which each of the tags is set is so adjusted that the receiver at the gate passed through is capable of receiving the identification signal a plurality of times from the same tag.
Accordingly, even if the receiver fails to receive identification signals produced at the same time in a certain cycle from tags passing through the same ingress-egress gate, the subsequent cycles comes around for the tags to produce identification signals again before the identification signal reception level lowers with the passage of the tags, so that the receiver is capable of receiving these identification signals at a sufficient reception level.
Thus, the ingress-egress monitoring system of the invention is usable for many persons to monitor their ingress into or egress from a specified area. Even if more than one person passed through one gate, the persons passing through the gate can be identified individually.